Rubber process and product



Patented Apr. 25, 1939 UNITED STATES PATENT OFFICE No Drawing.Application April 1, 1936, Serial No. 72,219. In Great Britain April 4,1935 9 Claims.

This invention relates to rubber processes and products in which rubberis manufactured in thread, filament or tape form.

Rubber may be manufactured in such form by extruding latex with orwithout other ingredients such as vulcanisers, accelerators, reinforcingfillers, anti-oxidants and stabilisers.

In my U. S. applications Nos. 34,855 and 40,859 I describe processes inwhich there is mixed with the latex or latex mixture for extrusionpurposes various setting agents, such as glue, gelatine and similarproteins, casein albumen or the like, natural and synthetic resins andgums which are water or alkali soluble, cuprammonium, cellulose etherswhich are water or alkali soluble, e. g. methyl cellulose andsubstances, inorganic or organic, which dissolve in water or dilutealkalies to give solutions which are miscible with latex. When the latexmixture is extruded or otherwise formed into thread by coagulating therubber, and dried, a set thread is produced, which may be woven orotherwise manipulated without the difiiculties associated withextensible threads.

In my U. S. applications Nos. 11,720, 15,340, 66,308, and 66,309processes are described in which rubber thread is provided aftercoagulation with a soluble or insoluble coating such as glue, gelatine,suitable cellulose derivatives, starch, wax, resin or the like, varnish,such as gum damar or copal, solutions of rubber or 1atex. By this meansthread with no, or only a limited stretch, is produced, which may beincorporated in fabrics without the difiiculties associated with themanipulation of extensible threads, and this thread may be renderedextensible in the case of the soluble coatings by dissolving the latterout.

The object of the invention is to improve or modify the threads or theprocesses described in the abovementioned specifications orapplications, and in this way to produce a thread with improvedproperties more particularly from the point of view, among other things,of strength and of the property of being non-hygroscopic.

I have discovered that a thread which has been formed from latex and asetting agent may be greatly strengthened by providing it with acoating, and, at the same time, the coating is better able to attachitself to the thread when this is formed of rubber with a setting agent.I may or may not dissolve out the coating and setting agent and in acase when I do not, but, on the contrary, render the coating, forinstance, gelatine insoluble by means of formaldehyde,

alum, potassium dichromate or the like, a thread will be produced whichwill be non-extensible and non-hygroscopic and suitable forincorporating in fabrics and if made with, at most, half the contentsrubber and compounding materials is very suitable for imitationhorsehair. I have found glue and gelatine to be very suitable settingand coating agents respectively.

The invention consists in a method for making thread which consists incoagulating a mixture of latex and setting agent and then applying acoating.

The invention also consists in a method as above, in which the settingagent is glue and the coating is gelatine.

The invention also consists in either of the methods as above, in whicha flexiser, for example glycerine, is incorporated with the coating.

The invention also consists in any of the methods as above, in which thethread is coated with cellulose acetate or the like whilst it is stilltacky.

The invention also consists in any of the methods as above, in which thethread is dyed at the same time as the setting agent and coating agentare removed.

The invention also consists in a method as in the preceding paragraph inwhich the thread is vulcanised at the same time as it is dyed.

The invention also consists in any of the methods as above, in which thesetting agent and the coating are removed, leaving a rubber thread,which may or may not have a small proportion of setting agent lefttherein.

The invention also consists in any of the methods as above, in whichdyestuif is mixed with the mixture of setting agent and latex.

The invention also consists in any of the methods as above, in whichdyestuif is mixed with the coagulating agent.

The invention also consists in the method of the first statement ofinvention, in which the coating is rendered insoluble.

The invention also consists in a modification of any of the processes asabove, in which the setting agent instead of being mixed with the latexis mixed with a coagulant for the latex.

The invention also consists in methods substantially as hereinafterdescribed.

The invention also consists in thread when made by any of the methods asabove.

The invention also consists in thread containing less than half rubberand. compounding materials for rubber, the remainder being setting agentand coating for example per cent.

or, at most, 45 per cent. rubber contents and compounding materials and55 per cent. or, at least, 55 per cent. glue and gelatine.

The invention also consists in thread substantially as hereinafterdescribed.

In carrying the invention into effect in one method by way of example, amixture is prepared as follows:

Revertexflu. 130

Sulphur 21.25 Zinc oxide 3.00 Accelerator 0.75 Agerite white 0.50 10 percent. casein solution 5.00

This mix is warmed slightly and to it is addedwhilst stirring iseffectedper cent. glue solution in such a quantity as will correspondwith 15 parts of dry glue to 85 of dry rubber. Such a composition isextruded warm or even hot into a coagulation bath comprising a warm orhot solution of the following formula;-

Acetone 85 Acetic acid 15 The coagulation bath solution need not ofnecessity be hot or warm but may also be cold and the extrusion orthread making point where the mix in thread form leaves the threadforming point is kept warm or hot or may be cold.

A thread prepared by extrusion and subsequent coagulation from a mixsuch as that above specifled, is dried or dried and vulcanised. Further,to obtain an improved thread it may after coagulation be run into a bathor through a bath of a liquid such as ethyl alcohol which will removethe majority of the water from the thread causing the precipitation ofthe glue. The thread after passing through or being left in the bath ofalcohol or similar liquid is then dried and, if desired, vulcanised. Thethread obtained using the second bath of alcohol is more limited instretch than that obtained using heat to remove the water, For thedrying of the thread after the treatment with alcohol a tunnel heated toa low temperature may be employed or the thread may be passed from thealcohol bath through starch or chalk or any suitable powdering agent,collected and allowed to dry at room temperature.

The coating may then be applied in any suitable way as by painting,spraying or otherwise, or the thread may be passed through a bath of thedesired liquid so that it picks it up in transit.

The thread may also be treated by coating a vulcanised or unvulcanisedthread under a desired degree of stretch for instance 20-25 per cent.with a suitable kind of soluble adhesive. Such an adhesive coating whichmay be a quick drying one may consist of glue, gelatine (equal parts byweight in water), a solution of a cellulose derivative, starch, moltenwax, resin or the like, or a suitable varnish such as gum damar orcopal. It may be applied by-coating, spraying or otherwise, before theprocess of weaving. The coating will be applied and allowed to dry tosuch a degree as will impart to the thread a rigid or semi-rigid set sothat the resulting thread will not possess the characteristic ofstretch, and is deprived of its elasticity or resilience as before.

As stated above, the adhesive used may be of such a character that itwill quickly dry, but if necessary the drying can be accelerated byartificial drying means of any kind.

The thread may be coated by suitable means (any known means) with acoating or skin of a gelatine solution, the strength of which may varyto a very great extent, say from 10 parts by weight of gelatine in 90parts of fluid (water) up to 75 parts of gelatine by weight and 25 partsof fluid (water) to which may be added according to requirements certainquantities of fiexiser, more especially glycerine, varying from 3 percent. (by weight) of the gelatine-water total up to 25 per cent. (byweight) of the gelatine-water total.

This gelatine coating may be dried in heat or in the ordinaryatmosphere; it may, whilst leaving the warm or hot gelatine bath orshortly thereafter, be run through a fine powder, such as talcum powder,French chalk or flour or the like, so as to render it non-tacky, makingit possible to wind it.

The thread can, if desired, be left partially soluble, leaving, afterdissolving most of the glue and gelatine, a rubber thread structurecapable after incorporation into fabrics by means of weaving, knittingor lacing and the like, of imparting to such fabrics a certain amount ofelasticity.

It is to be understood that the threads ready for weaving may compriseeither the uncoated or uncovered rubber itself, or may comprise thosewith a winding thereon of silk, cotton, or other fibrous material.

As regards dyeing, thin threads up to 8000 yards to the pound dye rightthrough fairly easily in the cold, but thicker ones will not get dyedright into the core unless prolonged boiling in dyestufi is given of atleast half an hour to one hour.

This is when this thread is still in the unvulcanised condition; whenvulcanised, the thread must be dyed by means of a cold process whenthere is a risk of over vulcanising the thread in the boiling process.

Practically the whole range of known dyestuffs may be used.

As regards vulcanisation, in the normal procedure a boiling out of thesetting agent will happen simultaneously with dyeing i. e., after theset and coated thread has been incorporated into fabric, i. e., in thegrey cloth, this grey cloth is then dyed by boiling, causing the threadto be dc-set, to become flexible and to become vulcanised at the sametime.

The vulcanisation takes place chiefly in the dyeing-boiling process whenthe yarn is already in the piece, but in many instances I also vulcanisethe thread after or before the gelatine coating has been applied so thatthe yarn, ready for weaving or knitting, is already vulcanised orsemi-vulcanised so that the subsequent boiling in the piece will eitherbe short and of not sufficient duration to influence vulcanisation or tobe so much as to complete the partial vulcanisation already given to thethread before its incorporation in the fabric.

Instead of being extruded the thread may be formed by a disc method forexample as in my U. S. applications Nos. 21,264 and 21,265, and in thecase of extrusion coagulant may be extruded into latex, and/or thesetting agent may be mixed with the coagulant as described in my U. S.application No. 40,859.

In a variation, the thread, when coming from the thread making machineand therefore in a Wet condition and tacky, may be coated with asolution of cellulose acetate or similar material, so as to coat thetacky thread with a very thin film of non-tacky material, whereby thethread on arrival at the end of the heating and drying apparatus isabsolutely non-tacky and can therefore be wound as required at oncewithout stretch if so desired either direct on to a Weaving pirn or inthe form of a cheese, bobbin or the like.

The application of the cellulosic or like coating renders the threadabsolutely non-tacky and it also prevents the thread from being rapidlyaffected by atmospheric moisture.

Various methods may be adopted for applying such film, for example:

(a) The thread may be run into a normal coagulant, then passed through adilute bath of cellulose acetate in acetone (about 5 per cent. strength)and then through a bath of water;

(1)) The thread may be run into a bath containing acetic acid, acetoneand the acetate, dispensing with water and allowing the heat in theheating chamber to dry off the solvents, thus leaving the surface in anon-tacky condition;

(0) The thread however prepared may be run through a normal coagulantpassed through the acetate solution and then dried by passing it througha drying chamber, or

(d) The thread may be run into the ordinary coagulant to which has beenadded a small quantity of acetate in acetone and then passing the threadthrough Water and then drying.

Other materials besides cellulose acetate may be used, for example,substances which can be dissolved in a volatile solvent and which may beeasily separated from such solvent by heat, chemical action or any ofthe known methods, and leaving a non-tacky film.

As examples there may be mentioned cellulose nitrate, viscose (to beprecipitated in dilute acids), cellulose ethers and cellulose esters.

The term latex includes aqueous dispersions of rubber, gutta-percha,balata or similar materials.

I claim:

l. A method of preparing rubber thread in a relatively inextensible formwhich comprises the steps of forming a thread from an aqueous dispersionof rubber containing a quantity of a removable lyophilic colloidsufiicient to reduce the extensibility of the thread, coagulating thethread, drying the coagulated thread, applying to such thread a solubleadhesive coating which will be inextensible when hardened, and hardeningthe coating.

2. A method of preparing rubber thread in a relatively inextensible formwhich comprises the steps of forming a thread from an aqueous dispersionof rubber containing a quantity of glue, sufficient to reduce theextensibility of the thread, coagulating the thread, drying thecoagulated thread, applying to such thread a coating of gelatine, andhardening the coating.

3. A method as claimed in claim 2 in which the thread containsapproximately 55% of glue and gelatine which are rendered insoluble.

4. A method of preparing rubber thread in a relatively inextensible formwhich comprises the steps of forming a thread from an aqueous dispersionof rubber containing a quantity of glue, sufficient to reduce theextensibility of the thread, coagulating the thread, drying thecoagulated thread, applying to such thread a coating of gelatinecontaining a plasticiser and hardening the coating.

5. A method of preparing rubber thread in a relatively inextensible formwhich comprises the steps of forming a thread from an aqueous dispersionof rubber containing a quantity of glue, sufiicient to reduce theextensibility of the thread, coagulating the thread, drying thecoagulated thread, applying to such thread a coating of a solution ofgelatine containing glycerine and hardening the coating.

6. A method of preparing rubber thread in a relatively inextensible formwhich comprises the steps of forming a thread from an aqueous dispersionof rubber containing a quantity of a removable lyophilic colloidsuificient to reduce the extensibility of the thread, coagulating thethread, applying a coating of cellulosic solution to the freshly formedthread and drying the coated thread.

'7. A method of preparing rubber thread in a relatively inextensibleform which comprises the steps of forming a thread from an aqueousdispersion of rubber containing a quantity of a removable lyophiliccolloid sufficient to reduce the extensibility of the thread,coagulating the thread, applying a coating of cellulose acetate solutionto the freshly formed thread and drying the coated thread.

8. A method of preparing a fabric in a relatively extensible form whichcomprises the steps of forming a thread from an aqueous dispersion ofrubber containing a quantity of a lyophilic colloid, sufficient toreduce the extensibility of the thread, coagulating the thread, dryingthe thread, applying a coating of soluble adhesive which Will beinextensible when hardened to the thread, hardening the coating,utilizing the thread to form a fabric and subsequently removing thelyophilic colloid and coating by means of a solvent therefor.

9. A method of preparing a fabric in a relatively extensible form whichcomprises the steps of forming a thread from an aqueous dispersion ofrubber containing a quantity of lyophilic colloid sufiicient to reducethe extensibility of the thread, coagulating the thread, drying thecoagulated thread, applying a coating of soluble adhesive which will beinextensible when hardened to the thread, hardening the coating,utilizing the thread to form a fabric and subsequently simultaneouslyremoving the lyophilic colloid and coating, and vulcanizing the threadby treatment of the fabric in a hot solvent for the lyophilic colloidand coating.

THOMAS LEWIS SHEPHERD.

